The present invention relates to coiled tubing units and an improved method and apparatus and carrying tool for the running of various tools off of coil tubing which require the application of a sudden downward force. Various devices are used to service oil and gas wells. Service applications can include running and pulling of safety valves, pack off assemblies and gas lift valves, the running of mechanical and electrically operated plugs in the well and setting them to repair or remove well head or surface equipment, or for any other reason, for example washing sand and debris off wireline tools, opening and closing sliding side doors, cutting paraffin, isolating tubing segments and repairing and testing tubing and setting through tubing bridge plugs.
Presently some of the above mentioned applications are performed by coil tubing units, and others by solid wireline equipment. Although a few applications can be performed by both, many advantages can be realized by using coil tubing units. For instance, the solid wireline units, in many cases, cannot be used to service a well. A wireline tool, which is suspended from the wireline, cannot be lowered down the well hole where there is an accumulation of debris or sand or deviation of a hole; one additional example is horizontal well completion. It should be understood that any reference to a downward force herein means downward relative to the "top" of a carrying tool attached to coil tubing, and therefore the "downward" force may actually be a horizontal shifting force rather than vertically downward.
A wireline does not have the strength of the coil tubing unit which might be necessary to pull a given device from the well. In these cases a work-over unit or snubbing unit must be used to rectify the problem. Work-over units or snubbing units are expensive solutions, and require extra men and equipment on standby.
U.S. Pat. No. 3,363,880 to Blagg describes a representative cable feeding apparatus, such as that used in the coil tubing unit services. U.S. Pat. No. 3,401,749 to Daniel describes a representative wireline apparatus. U.S. Pat. No. 4,612,984 to Crawford, and U.S. Pat. No. 4,682,657, also to Crawford, are illustrative of the many advantages of coil tubing units as compared to wireline units. The four mentioned Patents are hereby fully incorporated by reference.
As set out in the above referenced Patents, coil tubing units when provided with the proper carrying tools to run hollowed tools with internal flow bores into the well can perform several desireable functions such as washing debris and sand from the well to the "fishing neck", or "stuck" wireline tools; allowing contiguous circulation while jarring or pulling wireline type apparatus; and allowing continuous circulation, and thus equalized pressure when removing safety valves from the well (such as surface-controlled wireline retrievable tubing safety valves; for example, Otis Model DS, DK, DR "storm chokes" and equivalents). Fishing necks on such valves or tools can be grabbed with an off/on overshot, or releasable spear, such as manufactured by Baker Oil Tools. These tools may be hollowed with an internal bore to allow for circulation when used with the coil tubing units, as will be covered in more detail later.
During the removal of safety valves that are "stuck", the coil tubing unit can provide a much greater pulling capacity than a wireline saving the use of the much more expensive standby work-over rig snubbing unit necessary in the event the wireline unit cannot retrieve a stuck valve. Because of the possibility that a wireline could not retrieve a "stuck" valve (or any other tool), a snubbing unit or work over and standby workover crew and equipment is required for safety reasons when working off of a wireline to install and remove safety valves.
The Crawford U.S. Pat. Nos. 4,612,984, and 4,682,657 describe a method and apparatus to enable the running of jars, running tools and all pulling tools off of a coil tubing unit. During servicing operations on a well it may be desireable to install a variety of subsurface controls, for example, tubing safety valves, bottom hole regulators, packing devices, bridge plugs, and bottom hole chokes (here listed for illustration and not limitation). There are a variety of companies that provide such equipment. In general, the equipment is installed into the tubing by properly locating the device as follows. The device is configured into a certain external profile to correspond with an internal profile or landing in a nipple in the tubing string. The device is then run down the tubing string, until the profiles match, which precisely locates the device, after which it is installed. The common method for installing such safety valves comprises locating the device correctly and applying a directed force, either up or down depending upon the type of device, which releases a spring-loaded mechanism or equivalent in or on the device or tool, which further locates and locks the tool by expanding locking elements or dogs into corresponding concavities provided as part of the internal profile within the landing nipple. Additional impacts on the tool further expand a sealing element, and fully lock the device into place. Next a force is applied in the opposite direction from that required to set the device, to shear a pin and release the device from the wireline or tubing unit which can then be removed from the hole leaving the safety valve in position.
Although the earlier referenced Crawford Patents refer to jarring tools that can be run with a coil tubing unit, until the present invention it was not possible to apply a sudden downward force with a coil tubing unit. As can be readily understood by a study of the Blagg reference, the common method of forcing the tubing down the wellhead does not allow impulsive sudden application of downward force.
Generally, there are two types of devices or equipment installed in wells referred to in the industry as "X" equipment and "S" equipment. X equipment requires a downward force to locate and seat the device and an X device releases from the tubing string and carrying tool, or from the wireline, upon the application of force in the upward direction. S equipment, in contrast, requires upward force to locate and lock the device and the device releases from the setting tool upon the application of a force in a downward direction. Generally removal of X equipment requires application of a downward force, S equipment conversely requires application of an upward force. Because a coil tubing string cannot be suddenly moved through the injector head of a coil tubing feeding unit, prior to the present invention it was impossible to install X type equipment with a coil tubing unit because it was not possible to generate enough force in the downward direction to release the device. However, because of the relatively much higher tensile forces that can be applied through a coil tubing unit, relative to a wireline unit, coil tubing units are able to generate enough force in the upward direction to shear pines and release the tool. Therefore, although the method and apparatus of the referenced Crawford Patents allows application of a force in the upward direction, a sudden downward force or force sufficient to release X-type equipment and other downward force operated equipment is almost impossible to apply with coil tubing units primarily because of the drive mechanism and in some cases because of low weight of tubing above the valve, especially if the valve or other device is set in the nipple closest to the surface as is the usual case for safety valves.
The safety valve installation problem is illustrative of a problem existing during service operations on a well due to the need to have both a wireline unit and a coil tubing unit on standby, or to have both a wireline unit and a work-over unit on standby. The safety valve must be set at the end of each series of operations, for example, at the end of each day, or any time the service tools are pulled out of the well. The hole cannot be left in an open position, due to the danger of blow out and fire. The safety valve is in essence a stopper which must be put in and out in order to lessen the possibilities of a blow out. The present invention solves the problem by providing an apparatus, here named a shifting sub, which allows the application of a controlled and sudden downward force by a subsurface tool (or sub) which is run on a coil tubing unit. The force is sufficient to release the safety valve (or other device) from the coil tubing string, or to set equipment that requires downward force to set.
An additional example of downhole operations wherein the present invention presents great improvements is in the setting of plugs. Plugs are set to cement off or block off lower portions of a hole, in the case of closing a hole and abandoning it completely, or perhaps in the case of closing off the lower portion of a hole so that an upper formation can be worked. A plug is run in hole encased in a steel setting sleeve. A setting impulse is actuated which releases the plug from the sleeve and expands a basket. Steel slips will then hold the set plug in place while bridging material is run through the interior of the coil tubing unit. This bridging material includes, in most cases, lead shot for placement next to the basket of the plug and then a predetermined volume of cement. The present invention presents numerous advantages over the units run on wireline equipment, particularly because the cement dump bucket used with wireline equipment can carry only a very small volume of cement so that numerous runs are necessary to supply the needed volume of cement to plug a hole. When a plug is run on a coil tubing unit the volume of cement required is simply pumped through the coil tubing in one single continuous and much quicker operation. In effect, the contrast between a wireline cement dump bucket and the volume achievable through the coil tubing unit is like comparing a teaspoon to a dump truck.
Another application of the present invention would be for any operation that requires a detonation, for instance running a perforating gun sub. In general the way this is done now is that an actual explosive charge is set off which, in the manner of a detonator, sets off further shots perforating the steel casing to allow for production from a particular formation. The shifting sub of the present invention can replace the need for sending explosives down the well to act as the detonator. The present invention can simply be actuated by hydraulics to act as a firing pin or trigger to set off conventional perforating equipment.
Even though wireline equipment can be used to set safety valves and other equipment downhole, the process is a trial and error process with the setting tool (for example, Spang jar) attached to the wireline equipment simply lifted and dropped, lifted and dropped, et seq. until the device is released, and similarly lifted and dropped in order to set the safety valve. The operator has no precise control over the downward force being applied downhole, and in some instances the safety valve actually is not set correctly and can be blown out of the hole, unlike the controlled and directed precise force resulting from the apparatus and method of the present invention, which will be described in more detail below. In addition, a shifting sub constructed in this method can easily be removed from the hole and overhauled or modified to change the stroke or shearing force, unlike anything else in the art which has to be completely disassembled and overhauled to vary stroke or impact. Examples of other devices used in the field which must be disassembled for modification are those manufactured by Hipp which use a combination of hydraulics and preset and preloaded interior springs to provide a "jar" of indeterminate strength and stroke. These devices are described in U.S. Pat. Nos. 3,946,819 and 4,462,471.
A particular problem with retrieval of safety valves by wireline equipment is that the safety valves are of a larger diameter than the wireline equipment. When the wireline equipment is connected to a safety valve and the safety valve is pulled up the hole paraffin is trapped and builds up above the safety valve. The build-up of paraffin will cause the safety valve to become stuck, or at least can reach a magnitude greater than that possible to lift with a wireline. A safety valve attached to a coil tubing unit can simply be pulled up through the paraffin because of the much greater tensile stress a coil tubing unit can achieve.
One final example of the great benefit provided by the present invention is again related to the use of safety valves. As has been mentioned and will be mentioned in greater detail below, the many capabilities of a coil tubing unit, with provisions for adaptability and connection to any type of sub desired, has resulted in the use of coil tubing units on well sites, if for no other reason, because there are simply some things that cannot be done with a wireline unit. Safety considerations are paramount, and it is highly desirable to keep a safety valve installed in the well any time work is being done over the hole. Prior to the invention of the present apparatus and method, if the safety valve was of the type that could not be removed by a coil tubing unit the procedure that was followed was to have a wireline unit remove the safety valve and then have the coil tubing unit rig up over an open hole without the safety valve in place. The method and apparatus of the present invention provides a means of doing without the wireline unit altogether, rigging up over the hole with the coil tubing unit and shifting sub of the present invention, going downhole, removing the safety, pulling the safety valve completely out of the hole, removing it from the end of the coil tubing unit and the shifting sub, and then attaching the sub or downhole implement desired, and moving downhole with that instrument attached t the coil tubing unit to continue operations. This is a tremendous advance in safety due to the fact that the time spent working over an open hole without a safety valve in place is greatly reduced.